How do I end this story?

Hello. If you are still planning on finishing that story, I usually end my stores with these elements;
1) Sad twist
2) Dramatic referencing to earlier parts/characters
4) Excitement

And it is always great to keep in mind the small things before in the story, and how you expect the reader to read it. Because small things can make a big difference. More specifically, I would suggest Ben causes the main character to drown, but on accident. She dies thinking it was on purpose, and is angry. As a ghost she seeks out revenge, but don't make it obvious. This way you can make a part two, or leave it at a cliff hanger.

(Also, just you know in Ben's original story, he died at 11...)

its a fine title for a novel.for an intresting end have a minor-character turn out to be evil.this kind of twist never stops to amaze readers.

Throw one last curveball to the reader, even though the characters have been through almost everything, play with the readers sentiments one last time. Maybe a terminal Illness, a sudden death accident. Something along the lines of tragedy might work.

If you check the date of OP, it indicates a post from 3.5 years ago. Unfortunately, the OP is long gone and won’t benefit from your advice.